# -*- encoding: binary -*-
require 'io_splice_ext'

class IO

  module Splice

    # the version of IO::Splice, currently 2.0.0
    VERSION = '2.0.0'

    # The maximum default capacity of the pipe in bytes.
    # Under stock Linux, this is 65536 bytes as of 2.6.11, and 4096 before
    # We detect this at runtime as it is easy to recompile the kernel
    # and set a new value.
    # Starting with Linux 2.6.35, pipe capacity will be tunable
    # and this will only represent the default capacity of a
    # newly-created pipe.
    PIPE_CAPA = begin
      rd, wr = IO.pipe
      buf = ' ' * PIPE_BUF
      n = 0
      begin
        n += wr.write_nonblock(buf)
      rescue Errno::EAGAIN
        break
      end while true
      wr.close
      rd.close
      n
    end

    # copies the contents of the IO object given by +src+ to +dst+
    # If len is specified, then only len bytes are copied.  Otherwise
    # the copy will be until EOF is reached on the +src+.
    # +src+ and +dst+ must be IO objects or respond to +to_io+
    def self.copy_stream(src, dst, len = nil, src_offset = nil)
      src.kind_of?(String) and src = File.open(src, 'rb')
      dst.kind_of?(String) and dst = File.open(dst, 'wb')
      src, dst = src.to_io, dst.to_io
      rv = len
      src.sysseek(src_offset) if src_offset
      if src.stat.pipe? || dst.stat.pipe?
        if len
          while len > 0
            nr = len > PIPE_CAPA ? PIPE_CAPA : len
            nr = IO.splice(src, nil, dst, nil, nr, F_MOVE)
            if nr == 0
              raise EOFError, "unexpected EOF with #{len} bytes left"
            end
            len -= nr
          end
        else
          rv = 0
          begin
            nr = IO.splice(src, nil, dst, nil, PIPE_CAPA, F_MOVE)
            rv += nr
          rescue EOFError
            break
          end while true
        end
      else
        begin
          r, w = IO.pipe
          if len
            while len > 0
              nr = len > PIPE_CAPA ? PIPE_CAPA : len
              nr_src = copy_stream(src, w, nr)
              nr_src == nr or
                raise RuntimeError, "short splice from: #{nr_src} != #{nr}"
              nr_dst = copy_stream(r, dst, nr)
              nr_dst == nr or
                raise RuntimeError, "short splice to: #{nr_dst} != #{nr}"
              len -= nr
            end
          else
            rv = 0
            begin
              nr = IO.splice(src, nil, w, nil, PIPE_CAPA, F_MOVE)
              rv += nr
              begin
                nr -= IO.splice(r, nil, dst, nil, nr, F_MOVE)
              end while nr > 0
            rescue EOFError
              break
            end while true
          end
        ensure
          r.close
          w.close
        end
      end

      rv
    end

  end
end